1.3

• Adenosine Phosphates


  ATP, ADP, and AMP
• Adenosine Phosphates


  • AMP is one of the nucleotides present in RNA molecules
  • ADP and ATP differ structurally from AMP only in the number of phosphate groups present
• Hydrolysis of ATP and ADP

  1. ATP + H2O → ADP + Pi + energy

  2. ADP + H2O → AMP + Pi

  3. ATP + 2H2O → AMP + 2Pi
• Phosphoanhydride bond


  The chemical bond formed when two phosphate groups react with each other and a water molecule is produced
• Phosphoanhydride bonds in ATP and ADP


  They are very reactive bonds that require less energy than normal to break
• Conversion of glucose to glucose-6-phosphate

  Glucose + ATP → Glucose-6-phosphate + ADP
• Other nucleotide triphosphates


  • UTP (involved in carbohydrate metabolism)
  • GTP (involved in protein and carbohydrate metabolism)
  • CTP (involved in lipid metabolism)
• Flavin Adenine Dinucleotide (FAD)


  A coenzyme required in numerous metabolic redox reactions
• FAD


  • Can be visualized as containing either three subunits or six subunits
  • The active portion is the flavin subunit, which can be reduced to FADH2
• Redox reaction involving FAD

  Substrate with CH2-CH2 portion is oxidized to form C=C, FAD is reduced to FADH2
• Nicotinamide Adenine Dinucleotide (NAD)


  A coenzyme with functions similar to FAD in metabolic redox pathways
• NAD has a three-subunit or six-subunit structural representation, similar to FAD
• Removal of two hydrogen atoms


  Each removed hydrogen atom is equivalent to a hydrogen ion, H, plus an electron, e
• Oxidation-reduction reaction of flavin adenine dinucleotide (FAD)

  2H + 2e- + FAD ⇌ FADH2
• Nicotinamide Adenine Dinucleotide (NAD, NADH)

  Coenzyme functions in metabolic redox pathways, has a B vitamin as a structural component, can be represented structurally using a three-subunit or six-subunit formulation
• Three-subunit block diagram for NAD structure


  Nicotinamide - Ribose - ADP
• Six-subunit block diagram for NAD structure


  Nicotinamide - Ribose Phosphate - Adenine - Ribose Phosphate
• Positive electrical charge on NAD

  Due to the positive charge on the nitrogen atom in the nicotinamide component
• Reduction of NAD to NADH

  NAD+ + 2H + 2e- ⇌ NADH + H+
• Oxidation of a secondary alcohol to a ketone using NAD

  NAD+ accepts 2 hydrogen atoms and 2 electrons, forming NADH
• Coenzyme A (CoA-SH)


  Derivative of the B vitamin pantothenic acid, has a sulfhydryl group (-SH) in the ethanethiol subunit that is the active portion
• Three-subunit block diagram for CoA

  1. Aminoethanethiol - Pantothenic acid - Phosphorylated ADP
• Six-subunit block diagram for CoA

  1. Aminoethanethiol - Pantothenic acid - Phosphate - Adenine - Phosphorylated ribose - Phosphate
• Acetyl CoA


  Formed when an acetyl group bonds to the sulfhydryl group of CoA-SH through a thioester bond
• Classification of metabolic intermediate compounds

  • Intermediates for the storage of energy and transfer of phosphate groups
  • Intermediates for the transfer of electrons in metabolic redox reactions
  • Intermediates for the transfer of acetyl groups